This application is related to nitrous oxides sensors, methods of using nitrous oxides sensors, and related systems for use with combustion processes, for example in internal combustion engines and burner systems.
Nitrous oxides often form in internal combustion engines and burner systems under high temperature conditions. These are primarily NO, NO2 and N2O, and are collectively referred to as NOx. NOx formation is a particular issue in diesel engines, which run leaner and at higher compression ratios than typical spark ignition engines. These nitrous oxides, when released to the atmosphere, may combine with moisture to form nitric acid, leading to adverse health and environmental consequences. To combat this issue, modern engines and burner systems may be equipped with selective catalytic reduction systems which trap the NOx then react them with ammonia (NH3) to form N2 and H2O. This ammonia is typically introduced into the system in the form of urea (CO(NH2)2), which converts to ammonia when heated in the exhaust stream. Nitrous oxide sensors are used to control the performance of such systems. These nitrous oxide sensors are placed after the NOx trap (typically a Selective Catalytic Reduction (SCR) catalyst), and once NOx is detected, the system is triggered to purge the trap using the urea. These nitrous oxide sensors should be durable and be capable of detecting NOx in the 1 to 2000 ppm range, and not experience cross sensitivities to other gasses (H2, CO, sulfur and sulfur compounds, phosphorus and phosphorous compounds, etc. . . . ). Many NOx sensors on the market today are electrochemical sensors based on ion conductor technology; such NOx sensors have not proven satisfactory for all situations.
As such, there remains a need for alternative type of NOx sensors, and related systems and methods.